Inductive Z-Probe Bed Autoleveling: Working!

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Inductive Z-Probe Bed Autoleveling: Working!

Post by bill.gertz » Mon Mar 13, 2017 10:03 pm

This topic has been around the Forum for some time. I had some time between contracts and now have it working. Please be kind as this post is not yet complete, I'll be adding pictures and diagrams later. Modifying the Felix 3.0 or 3.1 for a inductive probe requires a bit of relatively simple work. The background on auto leveling is already documented by BoXZY at Inductive Probes and Repetier. The rest of this post is broken into four parts: Hardware, Electronics, Software and Calibration. First let's get the hardware out of the way.

You'll need our modified version of the extruder cover, a NPN NO Inductive Sensor and mounting hardware as shown in the bill of materials.
Bill of Materials
  • 1 each Inductive Sensor: SN4-04 NPN Normally Open (4.8 - 30v):
    There many suppliers for this sensor, use this one rated to 4.8v from IBB so it can be driven directly from the Felix ControlBoard
  • 1 each Modified Felix 3.0/ 3.1 Dual Head Extruder Cover
  • 1 each 3-Pin 2.54mm pitch Dupont Female Connector
    We salvaged ours from an old motherboard and soldered and used shrink tubing to connect the sensor cable
  • 2 each M3 x 20mm Hex Socket Button Head Screws
  • 2 each M3 Nut
  • 2 each M3 Washer
Start by printing the New Extruder Cover with at least .15mm resolution, with the front facing down to the bed. Since the part will be in a hot area, we suggest using ABS. You will need supports - we had the best luck with Simplify3D. Then lay the sensor in the cover sensor bed and pull the sensor cable through the axial holes in through the cover. Next, crimp or solder the Dupont female connector to the cable.
The schematic for the cabling is in the next section - electronics. Finally fit and screw in the new cover. You probably noticed that the cover doesn't fit like the original - you'll need to unscrew the extruder cooler fan screws from the extruder and thread them though the new cover before screwing them back in. This necessary so that the sensor platform doesn't move around. If the sensor moves in the slightest you'll lose the calibration and get poorly adhering prints.

The Inductive Sensor we used is an NPN NO type sensor. This means that the sensor operates as a normally open switch that conducts the load to ground when triggered. When used with the AVR AT Mega onboard the Felix ControlBoard, this will pull the attached pin to ground. As FelixRobotics was thinking ahead there are header pins prewired and ready to connect our sensor. These can be found on the ControlBoard on the upper left labeled OPT2. The enclosed software is configured to use Repetier Pin 45 (OPT2 Pins 5, 3 and 1) for the sensor. Connect as follows:
Sensor Wiring
  • Brown: +5v
    Pin 1 of OPT2 Header
  • Black: Repetier Pin 45
    Pin 3 of OPT2 Header
  • Blue: Ground
    Pin 5 of OPT2 Header
The LED on the sensor will turn on when it brought within 4mm or so from steel, copper or aluminum. Since the Felix Printer bed is aluminum the sensor will trigger somewhat closer than 4mm. You can test the sensor by holding a screw driver or other steel or aluminum tool near the bottom of the sensor - the LED should come on.

So now that the Hardware and Electronics are done, you'll need to update the software for the printer to use the inductive probe as the Z-min endstop and Z-probe for auto leveling.

The software for the Felix Printer 3.1 is attached. This software has been configured for the following options: More to come...
Repetier 0.92.9 (2017.02.19 Generated by Wizard).zip
(460.78 KiB) Downloaded 160 times
Last edited by bill.gertz on Fri Mar 17, 2017 3:14 pm, edited 5 times in total.

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Post by ErikL » Tue Mar 14, 2017 5:41 pm

As you know, the printbed is not built from solid steel. It's something light and I even tried different inductive sensors in the beginning: none of them were very accurate over the whole printbed.
Readings differ at the "holes" inside the plate compared to the places where everything is held together inside the printbed. This was causing issues when trying to print at a 0.05mm layer height.
I tried multiple inductive sensors and got the best results with a 8mm inductive sensor.

But I also wanted to add glass on top of the print bed (because of many advantages) and noticed that even a 14mm inductive sensor was unable to 'see' the printbed underneath a glass plate of 4mm thick. With a solid steel plate even a glass plate of 7mm is no problem at all but with these printbeds it's a problem...

Because of that I switch to the BLTouch sensor from geetech instead of an inductive sensor and I'm very happy with that one ;)

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Post by bill.gertz » Wed Mar 15, 2017 1:55 am

Great Erik! Any chance you could share your implementation? The firmware mods would be pretty much the same, except that the servo defs would need adding. The z-probe trigger wiring would be nearly the same. However the solinoid would need another pin, which did you find that worked? The other interesting bit for anyone else would be the z-probe mounting modification. Any chance you can document your mods and experience?

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Post by ErikL » Mon Mar 27, 2017 7:34 pm

I'm using pin 43 for z-probe and pin 47 for the servo. These pins are available on the OPT1 header and the pinout for OPT1 and OPT2 is documented in the forum.

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Post by sweetestpunch » Fri Apr 07, 2017 1:00 pm

Hi, new here from Australia, please let me know if the bed is same what sort of coverlet should I use?

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Post by bill.gertz » Mon Apr 10, 2017 4:15 pm

Hey sweetestpunch,

Are you asking me or Erik? I'm using the original 3.0 bed with Kapton sheet covering, and I think Erik is using glass over his. By coverlet, I think you mean the the extruder cover. Mine is included in the writeup above ... XhZdUlHeDA to pull the link apart.

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Post by Hardy123 » Sat Mar 07, 2020 8:41 pm

Hello have the Repetier FW for me and org. CAD File NEW EXTRUDER 6.5 ?
I Cant not Download this here is Delete;-(

thanks greets Hardy

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